This invention relates to a phase detector for electrical signals. In particular, it is a quadrature phase detector that has a small phase error over a large range of input signals with a constant phase-detector gain over that range.
A phase detector is an electrical circuit that produces a DC signal that provides a measure of the difference in phase between two input signals. Phase detectors are used in such electrical systems or items of equipment as phase-locked loops, analog correlators, adaptive filters, and clock recovery in digital systems, among others. Conventional phase detectors often exhibit inaccuracies over part or all of the range of variation due to circuit component tolerances. One means of minimizing these effects in past phase detectors has been to use precision temperature-compensated components. This increases the cost over that of a phase detector using conventional components. Another way of minimizing the effects of inaccuracies is to increase gain to make the detector output larger with respect to the inaccuracies. This often results in a detector gain which varies as a function of amplitude. This is undesirable when the phase detector is part of a control loop.
It is an object of the present invention to provide a better phase detector.
It is a further object of the present invention to provide a precision quadrature phase detector exhibiting a constant gain.
It is a further object of the present invention to provide precision quadrature phase detector having controllable offset voltages.
Other objects will become apparent in the course of a detailed description of the invention.